Dual mast system for simulation testing

ABSTRACT

A simulation testing system and method for testing an automobile system or component(s) such as an exhaust system ( 14 ) comprises first and second multi-axis simulation tables. One part of the exhaust system is supported by one of the tables with another part being supported by the other table. Each table includes hydraulic actuators ( 8 ) capable of imparting motion to the tables in a number of directions. The tables are independent from each other so that the motion imparted to one table can be distinct and separately controlled from that motion imparted to the other table. By arranging the tables so that the motions can vary between the two tables, more realistic simulation testing can be performed on the system or component being tested.

This application claims the benefit of provisional application SerialNo. 60/150,532 filed 25, 1999.

TECHNICAL FIELD

This invention relates to the art of simulation testing. In particular,the invention relates to a rig for simulation testing a full exhaustsystem for an automobile.

BACKGROUND

Durability testing of automotive parts is commonly used to determine thelifetime of the parts. Such testing has been conducted by placing thepart to be tested on a “durability automobile” and running thatautomobile over a test track under prescribed test conditions for aprescribed period of time. That type of testing, however, requires asignificant amount of time due to delays in assembling and schedulingthe durability automobile and delays caused by downtime attributed toother parts being tested on the same vehicle.

Simulation testing was developed to reduce the time required fordurability testing and thus to reduce the overall time required for newproduct development, reducing some new product cycles from as much asnine months to as little as one month. Simulation testing involvesplacing a part to be tested on a “rig,” which is designed to replicatethe motion of a durability vehicle to subject the part under test tothat motion without the problems incident to actual operation of thedurability vehicle. This is often accomplished by placing sensors atcritical places on the durability vehicle and recording the relativemotions at those locations. Then, the test rig is designed to replicatethose motions as exactly as possible.

A problem with simulation testing is that of correlation. That is, theresults obtained by simulation testing must correlate very well withthose obtained by durability vehicle testing for the simulation test toreplace the durability vehicle test. Design of a test rig to obtain thatcorrelation has not always been successful.

A prior art rig is that known as a MAST (multi-axis simulation table). Aknown MAST provides motions about six degrees of freedom, namely thethree Cartesian directions and roll, pitch and yaw about respective onesof those axes. The motions are provided in prescribed amounts, such as3.5-7 G's in the translation directions and 0-50 Hz frequency responseon all axes. Generally the system is controlled by a computer, andtwelve or more input channels from sensors on the equipment being testedare provided.

The prior MAST rig suffers from the limitation that it is generally arigid table (e.g., 60 inches by 84 inches) that subjects the entire partbeing tested to the same motions. In the field of automotive testing,however, applicant has discovered that such a rig can not adequatelyreplicate the motion of an extended part, such as an exhaust system, ona vehicle. Thus, the typical MAST rig does not provide adequatecorrelation.

Applicant has found that one reason for the lack of correlation providedby the known MAST rig when testing an elongate system, such as anexhaust system, is that the chassis of a vehicle flexes, resulting inmotions at one part of the chassis that differs significantly from thoseat the other end. Moreover, the fundamental frequency of a chassis isgenerally much lower than for other parts of an automobile.

SUMMARY OF THE INVENTION

In accordance with the invention, applicant has discovered thatsignificantly enhanced correlation can be obtained by mounting the partto be tested on multiple rigs, such as MAST's. In the preferredembodiment, two MAST rigs are used, with one part of the system beingtested being mounted on one and the remainder of the system on theother. While the multiple systems can be connected, such as by mountingone MAST on another, applicant's preferred embodiment provides twoindependent MAST rigs whereby the motion of the part on one MAST is notdependent on the motion of another MAST.

For example, when the system to be tested is an exhaust system, whichinvolves an engine with exhaust manifolds, catalytic converters,mufflers, and associated tubing, the engine and manifolds are mounted ona first MAST and the remainder of the system on a second, uncoupledMAST. This is accomplished in the preferred embodiment by providing twoMAST's longitudinally arranged on a floor.

Because each of the MAST's can be programmed separately, the motionsapplied to the engine and the mufflers can differ and can, therefore,come much closer to replicating the actual motion of the various partsof the durability vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a dual MAST rig in accordance with theinvention.

FIG. 2 is a side view of the rig shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the figures, a multiple-MAST full exhaust systemsimulation rig in accordance with the invention comprises a first MASTrig 2 and a second MAST rig 4 arranged adjacent each other and mountedon a common floor, such as the concrete floor of a test facility. Eachof the MAST rigs 2 and 4 is preferably capable of providing motionsabout six degrees of freedom. Because the rigs are not coupled, they maybe controlled separately to accommodate different motions of thedifferent parts of a vehicle for which the exhaust system is designed.

Each MAST includes a table 6 that is mounted for motion about sixdegrees of freedom. The tables are generally rigid and are connected toa plurality of computer controlled, hydraulic actuators to provide therequired motion. Three of the actuators 8 for each table are mounted forhorizontal motion, with two parallel and one perpendicular to theothers. At least three actuators 10 are provided beneath each of thetables for generating vertical, and pitch and roll motions.

In the preferred embodiment for use in testing an exhaust system, anengine 12 is mounted on a first of the MAST rigs and the tail pipehangers 14 are mounted to a second of the MAST rigs. By this arrangementthe vehicle motions on the engine are separated from those of thetailpipe, resulting in enhanced correlation.

The MAST rigs shown are those manufactured by MTS Systems of Loveland,Ohio, but the rigs may be of other types. The MAST rigs shown aregenerally capable of providing motions in the range of 0 to 50 Hz. In afurther modification of this arrangement, one of the MAST rigs isreplaced with a system that provides motions at higher frequencies, suchas that sold under the trademark CUBE, e.g., for mounting the engine.

I claim:
 1. A simulation test system comprising a first multi-axissimulation table and a second multi-axis simulation table, wherein thefirst and second multi-axis simulation tables are arranged to receiveseparate parts of a system to be tested and wherein each of the firstand second multi-axis simulation tables are controlled for movement ineach of six degrees of freedom.
 2. A simulation test system according toclaim 1 wherein said first and second multi-axis simulation tables areuncoupled.
 3. The simulation test system of claim 1, wherein eachmulti-axis simulation table has a plurality of actuators for moving eachof the tables, the actuators for one table being independent of theactuators of the other table so that movement imparted by actuators toone table can vary from movement imparted by actuators to the othertable.
 4. The simulation rest system of claim 3, wherein each of theplurality of actuators is hydraulically driven.
 5. The simulation testsystem of claim 1, wherein a first plurality of actuators are arrangedto provide a generally horizontal motion and a second plurality ofactuators are arranged to provide a generally vertical motion to eachmulti-axis simulation table.
 6. The simulation test system of claim 5,wherein the first plurality of actuators include two actuators that arealigned to impart a parallel generally horizontal motion, and oneactuator positioned impart a generally horizontal motion perpendicularto the parallel motion imparted by the two actuators.
 7. The simulationtest system of claim 1, further including an exhaust system comprisingan engine supported by one of the multi-axis simulation tables, at leastone exhaust pipe extending from the engine, and at least one exhaustpipe hanger supported by the other multi-axis simulation table.
 8. Thesimulation test system of claim 7, comprising a pair of exhaust pipes,and a pair of exhaust pipe hangers.
 9. A method for simulation testingcomprising providing first and second multi-axis simulation tables,mounting a first part of a system to be tested to said first multi-axissimulation table and mounting a second part of said system to be testedon said second multi-axis simulation table, wherein each of the firstand second multi-axis is simulation tables are controlled for movementin each of six degrees of freedom.
 10. A method according to claim 9,wherein said first and second multi-axis simulation tables areuncoupled.
 11. The method of claim 9, comprising subjecting each tableto movement through a plurality of actuators for durability testing ofthe system.
 12. The method of claim 11, wherein each actuator ishydraulically driven.
 13. The method of claim 9, wherein each tablesubjected to generally horizontal and generally vertical forces as partof said movement.
 14. The method of claim 13, wherein generallyhorizontal forces are applied in two directions, one direction generallyperpendicular to the other direction.
 15. The method of claim 14,comprising durability testing an exhaust system by mounting an engine ofthe exhaust system to one of the tables and at least one exhaust pipe ofthe exhaust system to the other of the tables.
 16. The method of claim9, comprising durability testing an exhaust system by mounting an engineof the exhaust system to one of the tables and at least one exhaust pipeof the exhaust system to the other of the tables.
 17. The method ofclaim 9, wherein one table is subjected to one set of movements and theother table is subjected to a different set of the movements for thesimulation testing.